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1.  Interleukin-5 receptor α levels in patients with marked eosinophilia or mastocytosis 
Background
Interleukin (IL)-5 plays a central role in the development and maintenance of eosinophilia and eosinophil activation in a wide variety of eosinophilic disorders. Although IL-5, IL-3 and GM-CSF can modulate expression of IL-5 receptor α (IL-5Rα) on eosinophils in vitro, little is known about soluble and surface IL-5Rα levels in vivo.
Objective
To assess surface and soluble IL-5Rα levels in patients with eosinophilia and/or mastocytosis.
Methods
Surface IL-5Rα expression was assessed by flow cytometry in blood and/or bone marrow from subjects with eosinophilia (n=39), systemic mastocytosis (n=8) and normal volunteers (n=28). Soluble IL-5Rα (sIL-5Rα) was measured in a cohort of 177 untreated subjects and correlated with eosinophilia, eosinophil activation, serum tryptase and cytokine levels.
Results
Whereas IL-5Rα expression on eosinophils inversely correlated with eosinophilia (r=−0.48, p<0.0001), serum levels of sIL-5Rα increased with eosinophil count (r=0.56, p<0.0001), serum IL-5 (r=0.40, p<0.0001) and IL-13 levels (r=0.29, p=0.004). Of interest, sIL-5Rα was significantly elevated in patients with systemic mastocytosis without eosinophilia. Although sIL-5Rα levels correlated with serum tryptase levels in these patients, eosinophil activation, assessed by CD69 expression on eosinophils and serum eosinophil-derived neurotoxin levels, was increased compared to normal subjects.
Conclusion
These data are consistent with an in vivo IL-5Rα regulatory pathway in human eosinophils similar to that described in vitro and involving a balance between surface and soluble receptor levels. This may have implications with respect to the use of novel therapeutic agents targeting IL-5 and its receptor in patients with eosinophilia and/or mastocytosis.
doi:10.1016/j.jaci.2011.05.032
PMCID: PMC3205313  PMID: 21762978
Hypereosinophilic syndrome; interleukin-5; mast cell; eosinophil; mastocytosis
2.  Role of breast regression protein 39 (BRP-39)/chitinase 3-like-1 in Th2 and IL-13–induced tissue responses and apoptosis 
The Journal of Experimental Medicine  2009;206(5):1149-1166.
Mouse breast regression protein 39 (BRP-39; Chi3l1) and its human homologue YKL-40 are chitinase-like proteins that lack chitinase activity. Although YKL-40 is expressed in exaggerated quantities and correlates with disease activity in asthma and many other disorders, the biological properties of BRP-39/YKL-40 have only been rudimentarily defined. We describe the generation and characterization of BRP-39−/− mice, YKL-40 transgenic mice, and mice that lack BRP-39 and produce YKL-40 only in their pulmonary epithelium. Studies of these mice demonstrated that BRP-39−/− animals have markedly diminished antigen-induced Th2 responses and that epithelial YKL-40 rescues the Th2 responses in these animals. The ability of interleukin13 to induce tissue inflammation and fibrosis was also markedly diminished in the absence of BRP-39. Mechanistic investigations demonstrated that BRP-39 and YKL-40 play an essential role in antigen sensitization and immunoglobulin E induction, stimulate dendritic cell accumulation and activation, and induce alternative macrophage activation. These proteins also inhibit inflammatory cell apoptosis/cell death while inhibiting Fas expression, activating protein kinase B/AKT, and inducing Faim 3. These studies establish novel regulatory roles for BRP-39/YKL-40 in the initiation and effector phases of Th2 inflammation and remodeling and suggest that these proteins are therapeutic targets in Th2- and macrophage-mediated disorders.
doi:10.1084/jem.20081271
PMCID: PMC2715037  PMID: 19414556

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